A mature student who researched serial killers as part of his PhD is being questioned by police about the murder of three women, it emerged today.

The man, named locally as Stephen Griffiths, 40, who is studying at the University of Bradford, was arrested on suspicion of the suspected murders of missing Suzanne Blamires, Shelley Armitage and Susan Rushworth.

Stephen Griffiths, 40. Photograph: Nicholas Razzell

West Yorkshire police today identified the remains of a woman whose body was found in the river Aire, in Shipley, West Yorkshire, on Tuesday, as Suzanne Blamires, 36, who went missing on Friday.

Armitage, 31, has been missing since 26 April, while 43-year-old Rushworth has been missing since June last year.

Police have been granted extra time, until this evening, to question Griffiths, who was arrested at his home on Monday.

Griffiths used a number of websites including MySpace, where he operated under the pseudonym Ven Pariah and username Ven99. He is also thought to have registered with the Guardian's dating site, Soulmates.

Guardian News and Media said today that the subscriber, whose username and profile picture were similar to those apparently used by Griffiths on other sites, had not been active on the site since April last year. He is believed to have been in contact with one other person, with whom the company said it was trying to get in touch.

The company said in a statement: "The safety of our members is paramount and, in line with our policy, the profile has been taken down while the police investigation is ongoing. All the information relating to the profile has been retained and we have notified the police."

Griffiths also used his Ven Pariah alter ego to comment on books and build a "wishlist" on the Amazon website.

Today a number of police officers, including forensic teams, have been at the scene where the remains were found, behind a car showroom about five miles from Bradford's red-light area.

CCTV footage is understood to be playing a large part in the investigation.

Officers accompanied by specially trained sniffer dog teams have been searching a number of buildings, some of them in the Chain Street area of the red-light district.

Rushworth was last seen at midday on 22 June last year, after getting off a single-decker bus near her flat on Oak Villas, in the city's Manningham area.

The grandmother and mother of three, who was known as Sue or Susie, suffered from epilepsy and was receiving help for her heroin addiction when she disappeared.

Police launched a poster appeal earlier this month to try to trace Armitage, who was last seen between the late evening of Monday 26 April and the early morning of the next day in Rebecca Street. Detectives described her as "a much-loved daughter and sister" and said her family were increasingly concerned for her welfare.

A police spokeswoman said Blamires had last been seen near her home in Allerton. She was considered at risk because of her work and her issues with alcohol and drugs.

Detectives have been trying to solve the murder of Rebecca Hall, a sex worker whose battered body was found in an alleyway in 2001, but today said they were not linking the disappearance of the three women to the 19-year-old, who also worked in Bradford.

A man who works close to Griffiths' flat said armed police arrived at the building on Monday. The man said: "He lives on the third floor. I've been told it's been completely sealed off now and everybody moved out.

"He was brought down and led away by the armed officers. [The police] have been all over the place."

The man said about six or seven years ago a woman's body was found behind the flats.